عزماته مثل النجوم ثواقبا لو لم يكن للثاقبات أفول
His resolutions are like piercing stars, if only those stars did not set.
Comparing lofty resolve to brilliant stars could be conventional. Here, however, the condition “if the stars did not set” changes the comparison: the resolutions must possess not only brilliance but endurance, while actual stars disappear from view in due course.
The audience first recognizes the familiar likeness and then asks why setting has been negated. That additional condition refines the praise and makes an ordinary comparison intellectually more distinctive.